As long as you follow the dilution sticky and make sure to void as many times as possible in that short time before you have before you go test. With a test that early you need to void at least 3-4 times before I would give them your diluted sample.
As far as holding it, it will not have any affect on the sample you are going to give. You will feel like you are going to piss your pants if you have to wait more than 20 minutes.